Inter-cell interference management is a challenge when designing wireless cellular networks. Inter-cell interference impacts the reuse of system resources such as time, frequency, codes and space, by limiting the spectral efficiency and received signal to interference noise ratio (SINR). Efficient management of inter-cell interference can improve coverage, quality of communication, or user experience, as well as the overall capacity of network resources.
A basic approach to tackle interference in wireless networks is to assign orthogonal channels to adjacent evolved Node Bs (eNBs). However, in order to increase spectral efficiency, in many cases networks are tending to become single frequency networks (SFN). Moreover, heterogeneous cellular networks allow a macro cell to coexist with a small cell such as a femto-cell or a pico-cell or a micro cell, increasing the complexity of inter-cell interference. Therefore, for both homogenous and heterogeneous networks, inter-cell interference has become more complicated.
Interference cancellation techniques generally rely on pilots transmitted by adjacent cells that are orthogonal or exhibit good autocorrelation and cross correlation characteristics to estimate the parameters associated with the desired signals and the dominant interferers. While such techniques may apply for time divisional multiple access (TDMA) systems such as the global system for mobile communication (GSM) or in coded division multiple access systems (CDMA), the techniques may not be particularly useful for orthogonal frequency division multiplexing (OFDM). In particular, in OFDM systems, the channel estimation typically spans only few sub-carriers depending on the frequency selectivity of the channel and hence gains from the averaging of interference due to cross correlation of the pilot sequences of two adjacent cells may not be realizable. This may lead to an inaccurate interference estimation and make subsequent interference rejection at the UE unreliable.